The present invention relates generally to implantable leads. More particularly, it pertains to leads having an extendable and retractable fixation mechanism.
Electrodes have been used to stimulate contraction of the heart or to reverse certain life threatening arrhythmias, where electrical energy is applied to the heart via the electrodes to return the heart to normal rhythm. Electrodes have also been used to sense and deliver pacing pulses to the atrium and ventricle. Cardiac pacing may be performed by a transvenous method or by electrodes implanted directly onto the epicardium. For transvenous pacing systems, a lead having an electrode is positioned in the right ventricle and/or in the right atrium through a subclavian vein, and the proximal electrode terminals are attached to a pacemaker which is implanted subcutaneously.
Some lead designs have xe2x80x9cfloatingxe2x80x9d electrodes or electrodes which are not attached to the endocardial wall of the heart. The floating electrodes lay in the blood pool or against the endocardial wall of the heart and the electrode may move slightly within the heart. Since the location of floating electrodes is not fixed with respect to the endocardial wall, the electrical performance of these electrodes varies and is generally less than optimal. Both the electrical sensing capability as well as the pacing delivery capability of such electrodes are suboptimal. The pacing parameters of such a floating electrode are also suboptimal. In addition, the floating electrodes can require increased voltage which unnecessarily drains the battery.
As an alternative to floating electrodes, leads have been provided with passive fixation elements that affix the electrode to the endocardial wall over time. With passive fixation elements, it can be difficult to determine whether the lead will affix in the location at which it is implanted.
Active fixation elements, such as a helix, have also been provided with distal ends of leads which allow a lead to be affixed to the endocardial wall. The helix is rotated to screw the lead into the endocardial wall. To rotate the helix toward and into the endocardial wall, a stylet is disposed within the lead and rotated. As the stylet is rotated however, the active fixation element may jump out of the end of the lead and damage tissue, and/or the helix. In addition, it is difficult for the implanter to determine how many turns to the stylet is necessary to advance the helix a certain distance.
A cardiac pacing system typically includes a pulse generator which supplies the electrical energy to the lead. The pulse generator may be implanted into a subcutaneous pocket made in the wall of the chest. A lead coupled with the pulse generator is routed subcutaneously from the pocket to the shoulder or neck where the lead enters a major vein, such as the subclavian vein, and into the heart. The proximal end of the lead is coupled both electrically and mechanically with the pulse generator. A distal end of the lead is placed within the heart, and a proximal end is placed within a pacemaker.
When leads with multiple conductors are involved, the conductors are individually and electrically coupled with the pulse generator at a proximal end of the multiple conductors. The multiple conductors at the proximal end are electrically insulated from each other to prevent shorts and limit electrical leakage between conductors. Medical adhesive is used to insulate the multiple conductors at the proximal end of the lead. However, the process of using medical adhesive is timely and costly to assemble. In addition, the medical adhesive bonds inconsistently, sometimes resulting in mechanical and electrical separation between the components.
The proximal end of the lead includes a terminal connection which provides the electrical and mechanical connection between the pacemaker and the proximal end of the lead. When inserted into the pacemaker, the components of the terminal connection undergoes axial stress as the implanter forces the proximal end of the lead into the pacemaker. After inserted, the implanter may pull on the lead to ensure the terminal end is sufficiently seated in the pacemaker, placing additional axial stress on the terminal connection.
Accordingly, there is a need for a lead with multiple conductors which are reliably insulated from one another. What is further needed is a lead having a terminal connection which can accommodate axial stress placed thereon.
An extendable and retractable lead includes a lead body which extends from a distal end to a proximal end. A conductor is disposed within the lead body and extends from the distal end to the proximal end of the lead body. In addition, the lead includes an electrode base coupled with the conductor proximate to the distal end of the lead body. The electrode base is threadingly coupled with an outer threaded shell. The electrode base includes external threads disposed thereon. The lead also includes an active fixation element coupled with the electrode base and the outer threaded shell.
In one embodiment, the lead includes a movement assembly which is configured to extend and retract the active fixation mechanism. The movement assembly includes a housing having an internally threaded portion and an externally threaded collar which is engaged with the internally threaded portion. In another embodiment, the movement assembly further includes an internally threaded insert disposed within the lead, where the threaded collar is engaged with the threaded insert.
In yet another embodiment, the outer threaded shell is formed of polyetheretherketone. Alternatively, the lead further includes a second outer shell coupled with the outer threaded shell, where the second outer shell forms a stop for the electrode base. In one embodiment, the second outer shell is formed of polyetheretherketone. The outer threaded shell is coupled with the second outer shell, for example, with epoxy. The epoxy comprises, in one embodiment, a mixture of one part EPOTEK 353ND to 1.75 parts EPOTEK 353ND-T. In yet another embodiment, the lead further includes a fluoroscopic ring disposed about the fixation helix.
A lead includes a lead body extending from a distal end to a proximal end. At least one conductor is disposed within the lead body and extends from the distal end to the proximal end of the lead body. An outer terminal ring is coupled with the lead body, and a sleeve is coupled with the outer terminal ring, and is also coupled with a terminal pin. The coupling allows for rotational movement between the outer terminal ring and the terminal pin. The sleeve is coupled with the outer terminal ring or the terminal pin with a snap-fit coupling. The snap-fit coupling, in one embodiment, comprises a first and second set of cantilevered hooks. In another embodiment, the snap-fit coupling comprises an annular flange received in a recess.
In another embodiment, a lead is provided which includes a lead body extending from a distal end to a proximal end. At least one conductor is disposed within the lead body and extends from the distal end to the proximal end of the lead body. An outer terminal ring is coupled with the lead body, and a sleeve is coupled with the outer terminal ring, and is also coupled with a terminal pin. The sleeve is coupled with the terminal pin with a snap-fit connection.
In yet another embodiment, a lead is provided which includes a lead body extending from a distal end to a proximal end. At least one conductor is disposed within the lead body and extends from the distal end to the proximal end of the lead body. An outer terminal ring is coupled with the lead body, and a sleeve is coupled with the outer terminal ring, and is also coupled with a terminal pin. The sleeve is coupled with the outer terminal ring or the terminal pin with a press-fit coupling.
A lead includes, in another embodiment, a lead body which is coupled with an outer terminal ring. The outer terminal ring is coupled with a terminal pin with a snap-fit connection. An insulator is disposed between the outer terminal ring and the terminal pin, and in one embodiment comprises a non-conductive coating. In one embodiment, the outer terminal ring is rotatably coupled with the terminal pin.
In yet another embodiment, a system includes an electronics system which has a pulse generator. The pulse generator is electrically coupled with a lead which includes a lead body extending from a distal end to a proximal end. At least one conductor is disposed within the lead body and extends from the distal end to the proximal end of the lead body. An outer terminal ring is coupled with the lead body, and a sleeve is coupled with the outer terminal ring, and is also coupled with a terminal pin. The coupling allows for rotational movement between the outer terminal ring and the terminal pin. The sleeve is coupled with the outer terminal ring or the terminal pin with a snap-fit coupling. The snap-fit coupling, in one embodiment, comprises a first and second set of cantilevered hooks. In another embodiment, the snap-fit coupling comprises an annular flange received in a recess. In yet another embodiment, the lead further includes a movement assembly which is configured to extend and retract an active fixation mechanism. The movement assembly includes a housing having an internally threaded portion and an externally threaded collar which is engaged with the internally threaded portion. In another embodiment, the movement assembly further includes an internally threaded insert disposed within the lead, where the threaded collar is engaged with the threaded insert.
The lead assembly described above provides several advantages, for example, ease of manufacturability is increased and through put times are reduced. The individual components can be snapped together, as opposed to waiting for messy bonding or long cure times. Bonding blocks, used for the bonding process, are eliminated, which are expensive, difficult and costly to clean. A consistent and increased strength of coupling is achieved using the snap fit design since bonding is variable based on the operator. Yet another advantage is that the geometry of the snap fit connector provides an insulation with a known thickness, which allows for a repeatable dielectric strength.
These and other embodiments, aspects, advantages, and features of the present invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art by reference to the following description of the invention and referenced drawings or by practice of the invention. The aspects, advantages, and features of the invention are realized and attained by means of the instrumentalities, procedures, and combinations particularly pointed out in the appended claims and their equivalents.